This invention relates to a method of locating a particle on a surface. For quality control and also research purposes, it is necessary to be able to evaluate the strength of a particle such as a diamond particle. A crushing machine is used for this purpose. In use, the particle to be tested is placed between opposed anvils, the anvils brought together and a load applied. The particle will fracture and crush at a given load and from the data derived therefrom the strength of the particle can be determined.
It is important in the practical operation of a machine of this nature that a single particle be accurately placed between the anvils. This may be achieved by use of a vacuum needle which picks up a sample from a source of the particles. Vacuum needles rarely pick up a single particle alone. The extra, unwanted particles may be removed by repeating the process of vibrating the needle and then passing the needle carefully over a prepared brush which physically removes stubborn particles.
The needle, now carrying the single particle, is moved to a target area where the vacuum is released. However, owing to the electrical or mechanical attraction between the particle and the needle the particle remains attached to the needle. A small jet of air may be used to dislodge the particle but this usually results in the particle bouncing away from the target area. A further problem with this method is that the positioning of the particle on the target area is random. The particle can end up on an edge or a flat surface, or a point and will not always be centrally located in the target area. This can affect the results which are obtained.